Rigid protection: Sturdy design constructed of an extra-strong polymer plastic shell and anatomically shaped uprights reinforce protection and support on both sides of your foot and ankle and facilitates a better fit.. Compression and comfort: Integrated pump mechanism easily inflates and deflates the pneumatic, soft foam/nylon liner for adjustable comfort and support.. Safe ambulation: Lightweight materials, rocker sole, durable tread pattern and inner/outer foam cushioning help absorb shock upon heel strike and promote a natural gait for a safe walking solution.. Hand washable. Medium fits those who wear men's shoe size 7½ – 10½ or women's shoe size 8½ – 11½..